A biometric is a measurement of any physical characteristic or personal trait of an individual that can be used to identify or verify the identity of that individual. Different forms of biometrics are well known and have been extensively tested. Common forms of biometrics include fingerprint, voice, eye scan (for example retinal scan and iris scan) face recognition, and others. Most biometric systems operate by initially enrolling individuals; that is collecting biometric samples from persons and using those samples to generate a template. The template is the data that represents the enrollee's biometric. The biometric system then matches new samples against the templates, and either verifies or identifies based on this matching.
Retinal scans and iris scans are extremely accurate, but may be considered intrusive by many people, since the scanner actually looks into the users eye. Moreover, the scan may require the user to cooperate, that is, it may require the user to look into the scanner in a certain way.
Fingerprint scans are also intrusive in that they require the user to put their hand into a fingerprint scanning device. In addition, the fingerprint scans often will not work on certain people who work with their hands (such as construction workers, and the like), and suffer from difficulties based on the actual orientation of the fingerprint. Moreover, if a user fails a fingerprint scan, there is no easy way to verify whether the user really should have failed that scan or not. Only highly trained individuals can manually match fingerprints. Finally, fingerprints require cooperation even more than retinal scans.
Face recognition has certain advantages in this regard. Initially, face recognition is not intrusive, since the face can be obtained by a simple camera, without requiring the user to do anything, other than walk by a location, and have their face captured by a camera. Similarly, face recognition does not require cooperation. Other face recognition systems may use lasers. While these latter techniques may be more intrusive, they are still no more intrusive than other technologies and do not require cooperation.
In addition, the human brain is extremely good at recognizing faces. An alarm allows a person to determine at a glance whether the face is correct or not.
The state-of-the-art in face recognition includes devices which are marketed by Viisage and Identix. These devices typically compare two-dimensional pictures of faces, against a two-dimensional template of another picture, which is stored in memory. The problem is that the comparison is intended to be a comparison of FACES, but the real comparison is a comparison of PICTURES OF FACES. Therefore, the comparison is highly affected by lighting, pose of the person, and other variances.